Mounds of Sand Stressed Minnesota Bridge

New York Times

WASHINGTON — The Interstate 35W bridge over the Mississippi in Minneapolis collapsed last August after construction workers had put 99 tons of sand on the roadway directly over two of the bridge’s weakest points, according to a National Transportation Safety Board report.

In the end, it's going to be a combination of poor design, poor maintenance, and poor repair planning.

When, exactly, is it ever a good idea to dump 99 tons of sand on an old bridge?